This invention generally relates to the testing of series connected cell assemblies of lead-acid storage batteries and in particular to the testing of such battery for short circuits between plates of opposite polarity within a cell and for electrical continuity between the cells of said battery.
In the manufacture of the usual multicelled lead-acid battery, the battery is assembled in a non-conductive case which is internally divided with a plurality of partitions depending upon the terminal voltage of the battery to be produced. For example, a standard 12 volt automotive battery has a non-conductive case which is divided into 6 separate cells by 5 such partitions. When the battery is assembled, each cell contains a plurality of interleaved positive and negative plates which after charging act to produce a voltage on the order of 2 volts. Thus, in order to form the 12 volt battery, these 6 cells must be connected together in series with the positive terminal of one cell being electrically connected to the negative terminal of an adjacent cell. In the newer types of automotive batteries, these connections are made by welding together lugs, one on either side of each cell partition through an aperture therein. At the ends of the series string are terminal post, one positive and one negative to which the external connections are made.
Two important criteria which should be determined after the plates have been assembled into the cells and the intercell electrical connections have been made are:
1. Whether there are any short circuits between plates of opposite polarity within a given cell; and
2. Whether or not there is electrical continuity as required between adjacent cells after appropriate electrical connections have been made.
A short circuit between plates of opposite polarity within a cell, would, of course, have a deleterious effect and quickly lead to a "dead" cell after charging. An open circuit on the series connection would produce an inoperative battery since, normally speaking, the only current path through the battery runs between the outside terminals which are located at the opposite ends of the series connection.
It is desirable to make the above recited short and open circuit tests before the battery cover is fastened to the container. Such detection of open and short circuits at this early stage would enable efficient repair, where possible, or eliminate the need for further processing where such repair proves to be impossible. One way of approaching this problem is to conduct the test with a dedicated test system which could be operated either by itself or in conjunction with other battery processing equipment, such as that used to conduct shear tests to detect weak welds after the intercell connections are made. However, no such system currently exits on the market. The subject invention is designed to correct this problem.